Relationship between Adrenal Cortex Pathology in Cushing's Syndrome and its Response to the Dexamethasone Suppression Test

Abstract

Cushing's syndrome is a severely disabling condition which can cause death if left untreated. Endogenous Cushing's syndrome can be ACTH-dependent or ACTH-independent. The ACTH-dependent type is more common and is usually caused by diffuse hyperplasia on the adrenal cortex. This study investigated the response to low- and high-dose dexamethasone suppression testing of 30 adrenalectomized patients with Cushing's syndrome, average age 37.3 ± 9.7 years. Twenty-four (79.3%) patients were female, and six (20.7%) were male. Bilateral adrenalectomy was performed in 14 (48.2%) patients and unilateral adrenalectomy (nine and seven right adrenalectomy) in 16 (51.8%). Two of the bilateral adrenalectomies were applied via endoscopic surgical approach. In the histopathological evaluation, diffuse hyperplasia was diagnosed in 13 (44.8%) patients and nodular hyperplasia in eight (26.6%), three macronodular and five micronodular hyperplasia. Adrenal cell adenoma was diagnosed in nine (28.6%) patients. Classic dexamethasone suppression testing was performed on all patients. Plasma levels of cortisol were not significantly decreased after low-dose testing, but plasma levels of cortisol were significantly decreased after high-dose testing in the diffuse hyperplasia group. In summary, due to the pathological changes of the adrenal cortex, dexamethasone suppression testing can differentiate between the two types of Cushing's syndrome.

Keywords

Adrenal cortex pathology Dexamethasone suppression test

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